Conventionally, a projection-type screen has been known in which image light is projected from a projector and in which moving images or still images are shown as reflected light on a screen. For example, recently in the fields of automobiles and the like, head-up displays have often been adopted in which instrument information such as speed, own-vehicle position information or the like is superimposed and displayed on the field of view of a driver, however, a problem to be solved is to achieve both transmission visibility and image visibility. In a display window such as a department store or at an event or the like, there is increasing demand to project and display images and moving images of product information, advertisement information and the like while maintaining the transparency of screens on which they are projected.
In order to cope with such a problem, for example, Patent Literature 1 discloses, as one method of an vehicle-mounted type head-up display, a display device 102 which uses a screen plate 101 subjected to half-mirror processing as shown in FIG. 6.
The screen plate 101 is formed with a half mirror (or a magic mirror) and the like which is arranged between the scene ahead and a user who visually recognizes it (in FIG. 6, the in-vehicle side of a front glass 103 of the automobile). The screen plate 101 used here is a plate the entirety of which is made translucent by uniformly forming an extremely thin reflective film over the entire surface of a transparent sheet made of, for example, glass or acrylic resin.
In the display device 102 disclosed in Patent Literature 1, since transparency is provided for light which is incident from the front of an observer in the direction of the observer (external light from the outside of the vehicle), and reflectivity is provided for light from the side of the observer (internal light within the vehicle), an image is projected from a projector 104 toward the half mirror, and thus the observer can also visually recognize the projected image while viewing the scene ahead.
As shown in FIG. 7, Patent Literature 2 discloses a reflection-type screen in which, in light diffusing layers 203 formed by vapor-depositing aluminum films 202 on black films 201, as transparent portions, through holes 204 are formed with a die-cutting device at regular intervals or randomly.
In the reflection-type screen disclosed in Patent Literature 2, since the light diffusing layers 203 and the through holes 204 which are the transparent portions are aligned at regular intervals or randomly, image light projected from a projector not shown in FIG. 7 is reflected off the light diffusing layers 203 so as to clearly show an image, and simultaneously, it is possible to visually recognize a background beyond the screen through the through holes 204.